Expandable vertebral implant

ABSTRACT

An expandable implant for engagement between vertebrae includes an inner member, an outer member, and a gear member positioned coaxial with respect to each other such that the inner and outer members are moveable relative to each other along an axis. The inner member includes a longitudinal groove configured to engage a pin extending through the outer member such that the pin prevents the inner member from translating completely through the outer member and aids in alignment and limits rotation of the second endplate. Portions of the implant may be provided with a series of markings such that when the markings are aligned, the implant is aligned in a specific configuration and for a specific implantation approach.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/313,623, filed Jun. 24, 2014, which is acontinuation-in-part of U.S. patent application Ser. No. 13/048,604,filed Mar. 15, 2011, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/758,529, filed on Apr. 12, 2010, now U.S. Pat.No. 8,282,683, the entire disclosures of which are incorporated hereinby reference in their entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates to a device to support the spine afterremoval of at least a part of a vertebra. In particular, the device maybe in the form of a multi-level implant which can replace multiplevertebral bodies.

BACKGROUND OF THE INVENTION

When a vertebra is damaged or diseased, surgery may be used to replacethe vertebra or a portion thereof with a prosthetic device to restorespinal column support. For example, vertebral body replacement iscommonly required in the treatment of vertebral fracture, tumor, orinfection.

In recent years, several artificial materials and implants have beendeveloped to replace the vertebral body, such as, for example, titaniumcages, ceramic, ceramic/glass, plastic or PEEK, and carbon fiberspacers. Recently, various expandable prosthetics or expandable cageshave been developed and used for vertebral body replacement. Theexpandable prosthetic devices are generally adjustable to the size ofthe cavity created by a corpectomy procedure and typically are at leastpartially hollow to accommodate bone cement or bone fragments tofacilitate fusion in vivo. Some expandable implants may be adjustedprior to insertion into the cavity, while others may be adjusted insitu. Two advantages of the vertebral body replacement using anexpandable prosthetic device that is adjustable in situ is that it iseasy to place or insert and it permits an optimal, tight fit by in vivoexpansion of the device. Some other advantages offered by an expandableprosthetic device are that they can facilitate distraction across theresected vertebral defect and allow immediate load bearing aftercorpectomy.

Instrumentation and specialized tools for insertion of a vertebralimplant is one important design parameter to consider when designing avertebral implant. Spinal surgery procedures can present severalchallenges because of the small clearances around the prosthetic when itis being inserted into position. Another important design considerationincludes the ability of the device to accommodate various surgicalapproaches for insertion of the vertebral implant.

SUMMARY OF THE INVENTION

According to one embodiment, an expandable prosthetic implant forengagement between vertebrae includes an inner member, a first endplate,an outer member, at least one pin, a gear member, and a second endplate.The inner member has a hollow interior portion and an external portionand includes a longitudinal groove extending along a length of the innermember. The first endplate is configured to engage a first vertebralbody and is connected to the inner member. The outer member has a hollowinterior portion configured to coaxially receive the inner membertherein. The inner and outer members are moveable relative to each otheralong a longitudinal axis. The pin has a first end and a second end andthe pin extends through the outer member such that the second end isconfigured to engage the groove in the inner member. The gear member ispositioned coaxial to the inner member and outer member and axiallyfixed to the outer member. The second endplate is configured to engage asecond vertebral body and is connected to the outer member.

The pin may protrude from an outer surface and/or an inner surface ofthe outer member. The pin may be configured to fit between a pluralitytabs on a distal end of the second endplate to aid in alignment andlimit rotation of the second endplate. The pin may engage with anuppermost surface of the groove to prevent the inner member fromtranslating through an opening in a proximal end of the outer member.The pin may be fixed to the outer member. The pin may be positionedtransversely to the outer member. The inner member may include a secondgroove configured to receive a second pin protruding from the outermember.

According to another embodiment, an expandable prosthetic implant forengagement between vertebrae includes an inner member having a hollowinterior portion and an external portion. A first endplate configured toengage a first vertebral body is connected to the inner member and thefirst endplate includes a first series of markings. An outer memberhaving a hollow interior portion is configured to coaxially receive theinner member therein. The inner and outer members are moveable relativeto each other along a longitudinal axis. A gear member is positionedcoaxial to the inner member and outer member and axially fixed to theouter member. A second endplate configured to engage a second vertebralbody is connected to the outer member and the second endplate includes asecond series of markings. When at least one of the first and secondseries of markings are aligned, the first and second endplates arealigned for a specific approach (e.g., anterior, etc.).

The first and second series of markings may include, for example,alphanumeric characters, numeric characters, colors, symbols, shapes,words, or pictures. The first series of markings may include a pluralityof different markings. The first series of markings may be positionedaround a perimeter of an extension portion of the first endplate. Thesecond series of markings may include a plurality of different markingswhich correspond to the first series of markings. The second series ofmarkings may be positioned around a perimeter of the second endplateproximate to a plurality of tabs that connect the second endplate to theouter member. A third marking may be provided on the inner or outermembers to aid in alignment of all of the components of the implant.

The implant may also include a locking member configured to restrictrelative movement between the inner member and the outer member. Thelocking member may be configured to be received in the outer member. Thelocking member may include an engagement member that engages the gearmember to prevent rotation of the gear member. The engagement member mayengage a cutout formed in the gear member to prevent rotation of thegear member. The gear member may include gear teeth extending around aperimeter of the gear member. The gear teeth may extend from a proximalend of the gear member to a distal end of the gear member.

According to another embodiment, an expandable prosthetic implant forengagement between vertebrae includes an inner member having a hollowinterior portion and an external portion and the inner member includes alongitudinal groove extending along a length of the inner member. Afirst endplate is configured to engage a first vertebral body and isconnected to the inner member. The first endplate includes a firstseries of markings. An outer member having a hollow interior portion isconfigured to coaxially receive the inner member therein. The inner andouter members are moveable relative to each other along a longitudinalaxis. A pin having a first end and a second end extends through theouter member. The second end of the pin is configured to engage thegroove in the inner member. A second endplate is configured to engage asecond vertebral body and is connected to the outer member. The secondendplate includes a second series of markings. A gear member ispositioned coaxial to the inner member and outer member and axiallyfixed to the outer member. A locking member is configured to restrictrelative movement between the inner member and the outer member. Thelocking member is configured to be received in the outer member. When atleast one of the first and second series of markings are aligned, thefirst and second endplates are aligned for a specific implantationapproach.

According to another embodiment, an expandable prosthetic implant devicefor engagement between vertebrae generally includes an inner member,outer member, and gear member positioned coaxial with respect to eachother such that the inner and outer members are moveable relative toeach other along an axis. The inner member has a hollow interior portionand a threaded external portion and includes a first end portionconfigured to engage an endplate which is capable of engaging a firstvertebral body. The outer member has a hollow interior portionconfigured to receive the inner member and includes a second end portionconfigured to engage an endplate which is capable of engaging a secondvertebral body. The gear member is axially fixed to the outer member andfreely rotatable with respect to the outer member and the gear memberthreadedly engages the threaded portion of the inner member.

The implant is configured to engage the vertebrae such that first andsecond end portions are oriented in a predetermined alignment withrespect to the first and second vertebral bodies. The gear memberincludes teeth extending around the perimeter of the gear member and theteeth are exposed to the exterior and configured to be accessible by atool member.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more readily understood with reference tothe embodiments thereof illustrated in the attached drawing figures, inwhich:

FIG. 1 is a perspective view of an implant in accordance with anembodiment of the present invention;

FIG. 2 is an exploded view of the implant of FIG. 1;

FIG. 3 is a cross-sectional view of the implant of FIG. 1 taken alongline 3-3 of FIG. 1;

FIG. 4 is perspective view of an embodiment of an inner member of theimplant of FIG. 1;

FIG. 5 is perspective view of an embodiment of an outer member of theimplant of FIG. 1;

FIG. 6 is an elevated perspective view of one embodiment of a gearmember of the implant of FIG. 1;

FIG. 7 is a bottom perspective view of the gear member of FIG. 6;

FIG. 8 is a perspective of one embodiment of a tool according to thepresent invention;

FIG. 9 is a cross-sectional view of the tool of FIG. 8 shown engaging anembodiment of an expandable implant according to the present invention;

FIG. 10 is a perspective view of another embodiment of an implantaccording to the present invention; and

FIG. 11 is a perspective view of another embodiment of an endplate of animplant according to the present invention;

FIG. 12 is an exploded view of the endplate of FIG. 11;

FIG. 13 is a cross-sectional view of the endplate of FIG. 11;

FIG. 14 is an exploded view of another embodiment of an implantaccording to the present invention;

FIG. 15 is perspective view of an embodiment of an outer member of theimplant of FIG. 14;

FIG. 16 is a perspective view of one embodiment of a gear member of theimplant of FIG. 14;

FIG. 17 is a perspective view of one embodiment of a gear member with anengagement element of the implant of FIG. 14;

FIG. 18 is a perspective of one embodiment of a tool according to thepresent invention;

FIG. 19 is a cross-sectional view of the tool of FIG. 18 shown engagingan embodiment of an expandable implant according to the presentinvention;

FIG. 20 is an exploded view of an implant according to anotherembodiment;

FIGS. 21a and 21b are close-up side views of the embodiment shown inFIG. 20; and

FIGS. 22a and 22b are close-up cross-sectional views of the inner andouter members shown in FIG. 20.

Throughout the drawing figures, it should be understood that likenumerals refer to like features and structures.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the invention will now be described withreference to the attached drawing figures. The following detaileddescription of the invention is not intended to be illustrative of allembodiments. In describing preferred embodiments of the presentinvention, specific terminology is employed for the sake of clarity.However, the invention is not intended to be limited to the specificterminology so selected. It is to be understood that each specificelement includes all technical equivalents that operate in a similarmanner to accomplish a similar purpose. The features of one embodimentmay be employed with other embodiments as the skilled artisan wouldrecognize, even if not explicitly stated herein.

Referring to FIGS. 1-6, a preferred embodiment of an expandablevertebral implant 10 is shown. The implant 10 preferably comprises aninner member 12 which may be telescopingly received within an outermember 14. The implant 10 further comprises a gear member 16 generallyconfigured to effect translation of the inner member 12 with respect tothe outer member 14 thereby allowing for expansion and contraction ofthe implant 10. The inner member 12, the outer member 14, and the gearmember 16 are preferably centered along a longitudinal axis 18 anddefine a hollow interior portion which may be filled with bone material,bone growth factors, bone morphogenic proteins, or other materials forencouraging bone growth, blood vessel growth or growth of other tissuethrough the many apertures in the device. In one preferred embodiment,members 12, 14, and 16 are made of a polyether ether ketone (PEEK)plastic material. There are several known advantages of PEEK plasticmaterial including being radiolucent, having a mechanical strength thatis close to bone, and may be more easily sterilized than other plastics.In alternate preferred embodiments, the members 12, 14, and 16 may bemade of a biologically inert metal alloys, such as titanium, or othersuitable materials.

Referring to FIGS. 1-5, the inner member 12 has a generally cylindricalbody 24 with a distal end 22 and a proximal end 36. In a preferredembodiment, the body 24 of the inner member 12 comprises an innersurface 28 and an outer surface 30 and generally defines a hollowinterior portion 23 extending axially therethrough. At least part of theouter surface 30 preferably includes external threads 32. Locatedproximate to the distal end 22 of the body 24 are a plurality of tabs 38which assist in connecting and positionally locating an endplate 20. Ina preferred embodiment, the body 24 is configured and dimensioned to becooperatively received within outer member 14.

The outer member 14 has a generally cylindrical body 40 with a distalend 42 and a proximal end 44. In a preferred embodiment, the body 40 ofthe outer member 14 comprises an inner surface 46 and an outer surface48 and generally defines a hollow interior portion 50 extending axiallytherethrough. The outer surface 48 preferably has at least one slot 52and an opening 54 configured and dimensioned to receive a portion of animplantation tool. In a preferred embodiment, the opening 54 extendsfrom the outer surface 48 to the hollow interior portion 50 and at leasta portion of the opening 54 is threaded. As best seen in FIG. 5, theinner surface 46 includes a channel 57 for receiving a locking member(discussed below). Located proximate to the proximal end 44 of the outermember 14 are a plurality of tabs 60 which assist in connecting andpositionally locating an endplate 62. In a preferred embodiment, a lip162 is formed around the exterior of the distal end 42 of body 40 and isconfigured to cooperatively fit with a portion of the gear member 16. Aplurality of relief spaces or slots 64 are radially spaced around lip162 to facilitate a snapping engagement of the lip 162 with the gearmember 16. In this regard, slots 64 allow the lip 162 to deform slightlyand contract in the radial direction to accommodate gear member 16 tosnap on to lip 162. In a preferred embodiment, the interior portion 50of body 44 is configured and dimensioned to cooperatively receive body24 of inner member 12 within outer member 14. In this regard, thedimensions of interior portion 50 of body 44 are greater than dimensionsof body 24 of inner member 12.

As best seen in FIGS. 2-5, in a preferred embodiment of a prostheticdevice 10, the body 24 of the inner member 12 includes a flattenedportion 34 which extends at least in part from the distal end 22 to theproximal end 36 and includes a base member 37 having at least one lobe39 located proximate to the distal end 36 of the body 24. Focusing onFIG. 5, the body 40 of the outer member 14 includes a flattened area 56and at least one depression 58 on the inner surface 46. When the innermember 12 is assembled within the outer member 14, the flattened area 56of the outer member 14 cooperatively aligns with the flattened portion34 of the inner member 12 and the at least one depression 58 of outermember 14 receives the at least one lobe 39 of the inner member 12. Theflattened portion 34 and the flattened area 56 along with the lobes 39and the depressions 58 cooperate to allow the inner member 12 tolinearly move with respect to the outer member 14 but prevent the innermember 12 from rotating with respect to the outer member 14. Inaddition, the base member 37 serves as a stop preventing the innermember 12 from rotating to a point of disengagement from outer member14.

Referring now to FIGS. 6-7, a gear member 16 comprises a generallyhollow body 164 extending from a distal end 66 to a proximal end 68 witha helical thread 70 along at least part of an inner wall 72 and an arrayof gear teeth 74 along a portion of the exterior wall 75. The gearmember 16 is generally configured to rotatably connect to the distal end42 of the outer member 14 and the internal helical thread 70 isconfigured to engage the external threads 32 of the inner member 12 tocause translation of the inner member 12 with respect to the outermember 14. In a preferred embodiment, the gear member 16 includes acylindrical cutout feature 76 extending around the inner wall tocooperatively receive the lip 54 of the outer member 14. In this regard,the gear member 16 may rotate freely with respect to the outer member 14while being retained from longitudinal and lateral movement. In apreferred embodiment, the gear member 16 also includes a series ofcutouts 73 located proximate to the proximal end 68 for engaging aportion of a locking member.

With continued reference to FIGS. 6-7, the gear teeth 74 extendsubstantially from the proximal end 68 to the distal end 66 and extendaround the entire periphery of at least a portion of the exterior wall75. The outer-most external diameter 78 of the gear member 16 is sizedto be the same as or slightly smaller than the smallest outer diameterof the endplates 20, 62 and the outer member 14. In this regard, whenthe implant 10 is viewed from the end in a plane perpendicular to thelongitudinal axis 18, the gear member 16 does not protrude radiallyoutward from beyond the perimeter of the endplates 20, 62.

As shown in FIG. 7, in a preferred embodiment, the gear teeth 74 extenda width 180 in a generally radial direction and generally extendradially outward to the outer diameter of the gear member 16. In thisregard, the teeth 74 may be designed to have a width 180 to accommodatethe expected gear forces given the particular gear ratio, types ofmaterial used, and desired overall diameter of prosthetic device 10. Oneskilled in the art will appreciate that the larger the outer diameter towhich the teeth 74 radially extend, the larger the teeth 74 may bedesigned while still maintaining the same gear ratio. In this regard,when the teeth 74 are made larger, they generally have a bettermechanical strength. Also, the ability to design larger, wider, andstronger teeth 74 is advantageous for embodiments where the implant 10is made of PEEK, other plastic, or other non-metallic materials that mayhave less mechanical strength than, for instance, titanium.

Furthermore, as described in one embodiment, because the outer-mostdiameter of the gear member 16 may be as large as the outer diameter ofthe endplates 20, 62, and the teeth 74 extend radially to the outer-mostdiameter of the gear member 16, a larger inner diameter of the gearmember 16 may be manufactured without compromising mechanical gearstrength. As a result, a larger overall inner diameter of the implant 10may be accommodated which allows the packing of more bone materialtherein and facilitates bone fusion once the implant 10 is implanted.

As seen in FIGS. 1-3, in a preferred embodiment, the teeth 74 areexposed to the exterior of prosthetic device 10. Because the teeth 74are exposed around the periphery, little to no material is needed tocover up the exposed teeth, which generally makes the implant 10 lighterand easier to manufacture than prior art devices that require coveringthe gear teeth. In addition, the gear member 16 is more easily visibleby a surgeon and more readily accessible by a rotation tool than devicesthat hide or cover gear teeth.

Referring to FIGS. 2, 5, and 7, in a preferred embodiment, the implant10 also includes a locking member 80. The locking member 80 may beprovided to substantially restrict all relative movement between innermember 12 and outer member 14, when, for example, the desired expansionof the prosthetic device 10 has been obtained. The locking member 80 hasa body portion 82 with a through-hole 84. In a preferred embodiment, thebody portion 82 has at least one, but preferably two, outwardlyextending, flexible arms 86, 88 and at least one engagement member 90.In other preferred embodiments, instead of flexible arms 86, 88, it iscontemplated that the locking member 80 may include an alternate biasingmember, such as a leaf spring. The locking member 80 is configured anddimensioned to be received in the channel 57 of the outer member 14 insuch a manner that the arms 86,88 rest against a shelf portion in thechannel 57 and the through-hole 84 partially aligns with opening 54. Theengagement member 90 preferably protrudes upwardly and is configured anddimensioned to engage the cutouts 73 of the gear member 16 to preventthe gear member 16 from rotating.

Referring now to FIGS. 1-3, in a preferred embodiment, the endplates 20,62 are shown wherein the endplate 20 connects to the inner member 12 andendplate 62 connects to the outer member 14. In a preferred embodiment,endplate 20 includes an extension portion 91 which is received in theinterior portion 23 of inner member 12, for example, in an interferenceor snap fit and includes a plurality of tabs 93 which interdigitate withtabs 38 to connect and position endplate 20 with respect to the innermember 12. Endplate 62 includes an extension portion 95 which engagesthe proximal end 44 of the outer member 14, for example, in aninterference or snap fit and includes a plurality of tabs 97 whichinterdigitate with tabs 60 to connect and position endplate 62 withrespect to the outer member 14. The endplates 20, 62 also preferablyinclude hollow interior portions 99, 101 which are in fluidcommunication with the hollow interior portions 23, 50 of inner member12 and outer member 14, respectively.

In a preferred embodiment, each endplate 20, 62 is generally annular inshape when viewed from the end or perpendicular to the longitudinal axis18. It is, however, contemplated that the endplates 20, 62 can be othershapes including oblong, elliptical, kidney bean, polygonal, orgeometric. Preferably, the endplates 20, 62 are designed to resemble ormimic the footprint of the vertebral body to which the endplates willengage. In this regard, endplates 20, 62 are configured to engageportions of the vertebrae in a predetermined orientation to maximizecontact of the superior surface of the endplates 20, 62 with bone.

The dimensions of endplates 20, 62 can be varied to accommodate apatient's anatomy. In some embodiments, the endplates 20, 62 have awedge-shaped profile to accommodate the natural curvature of the spine.In anatomical terms, the natural curvature of the lumbar spine isreferred to as lordosis. When implant 10 is to be used in the lumbarregion, the angle formed by the wedge should be approximately between3.5 degrees and 16 degrees so that the wedge shape is a lordotic shapewhich mimics the anatomy of the lumbar spine. In alternate embodiments,the wedge shape profile may result from a gradual increase in heightfrom an anterior side to a posterior side to mimic the naturalcurvature, kyphosis, in other regions of the spine. Thus, in otherembodiments, the angle may be between about −4 degrees and −16 degrees.

As shown in FIGS. 1-3, in a preferred embodiment, the endplates 20, 40include a plurality of mounting holes 92 spaced around the perimeter ofeach endplate 20, 40 for receiving insertable bone engaging members 94.In one embodiment, bone engaging members 94, comprise conical spikes 96each having a cylindrical base portion 98 configured to fit within holes92, for instance, by press-fit or by threaded engagement. In alternateembodiments, differently shaped bone engaging members 100 may be used,or in other embodiments no bone engaging members may be used. Referringagain to FIG. 2, according to one embodiment, endplates 20, 62 havechamfered edges 100 around the perimeter to facilitate insertion and/oraccommodate the shape of the vertebral bodies which they engage. Thesuperior or bone engaging surfaces 102, 104 of endplates 20, 62 may alsoinclude numerous types of texturing to provide better initial stabilityand/or grasping contact between the end plate and the respectivevertebrae. In a preferred embodiment, the texturing is a plurality ofteeth 106. In preferred embodiments where the implant 10 is manufacturedfrom PEEK or other plastic materials, the endplates 20, 62 may alsoinclude radio-opaque material, such as tantalum markers 108, which aidin providing location markers in radiographic images.

In preferred embodiments, the length, diameter, and shape of prostheticdevice 10 may vary to accommodate different applications, differentprocedures, implantation into different regions of the spine, or size ofvertebral body or bodies being replaced or repaired. For example,implant 10 may be expandable to a longer distance to replace multiplevertebral bodies. Also endplates 20, 62 can be sized and shaped as wellas positioned to accommodate different procedures and approached to thespine. For example, endplates 20, 62 may be made smaller for smallerstatured patients or for smaller regions of the cervical spine. Inaddition, it is not required that endplates 20, 62 be shaped and sizedidentically and in alternate embodiments they can be shaped or sizeddifferently than each other and/or include different bone engagingmembers or texturing.

Turning now to FIGS. 8-9, the implant 10 may be expanded by a tool 110that includes a gear member 112 at its distal end 114. The tool 110extends along a tool axis 114 and in operation the tool 110 isconfigured to engage the implant 10 such that the tool axis 114 isgenerally perpendicular to the longitudinal axis 18. The gear member 112is configured to engage teeth 74 of the gear member 16 such that whenthe gear member 112 is rotated about the axis of the tool 110, the gearmember 16 of the implant 10 is rotated about the longitudinal axis 18and the inner member 12 translates along the longitudinal axis 18 toeither expand or contract the implant 10. In a preferred embodiment, thetool 110 may include a central shaft 116 having a threaded distal tipportion 118 that extends distally beyond gear member 112 to facilitatelocation and mounting of tool 110 with the implant 10. The threadeddistal tip portion 118 preferably includes a generally conical endportion and may be configured to extend radially through the opening 54and threadably engage opening 54 in the outer member 14.

With continued reference to FIGS. 8-9, in one embodiment of prostheticdevice 10 at least one, but preferably a plurality of mounting featuresor slots 52 are provided along the outer surface 48 of outer member 14.The tool 110 includes at least one, but preferably two, articulatingarms 120, 122 that engage slots 52 for better engagement of the tool 110with the implant 10 during insertion of the implant 10. In anotherpreferred embodiment, the tool 110 may include arms 120, 122 that do notarticulate.

In an exemplary use of the tool 110 with the implant 10, the tool 110initially engages the slots 52 of the implant 10 via the arms 120, 122and gear member 112 engages gear member 16 via their respectiveinterdigitating teeth. A control member on the proximal end of the tool110 (not shown) is manipulated to advance the central shaft 116 towardopening 54. The threaded tip portion 118 enters into opening 54 engagingthe threads in opening 54 as well as engaging the through-hole 84 oflocking member 80. It is also contemplated that the central shaft 116 isnot movable with respect to the tool 110. In that embodiment, the entiretool 110 is moved so that the central shaft can enter and engage theopening 54 and the through-hole 84. As discussed earlier, thethough-hole 84 is offset from opening 54, thus, when threaded tip 118engages and advances into the opening 54 and the through-hole 84, thelocking member 80 is pulled downwardly, riding along the conical edge ofthe tip 118 until the through-hole 84 is aligned with the opening 54. Asthe locking member 80 is pulled downwardly, the arms 82, 84 are flexedand the engagement member 90 disengages from the cutout 73 of the gearmember 16 allowing the gear member 16 to rotate freely. The gear member112 of tool 110 is then rotated via opening 114 which, in turn, rotatesgear member 16. As discussed above, the rotation of gear member 16results in the movement of inner member 12 causing the implant 10 toeither expand or contract, depending on the direction the gear member 16is rotated. Once the desired height for implant 10 is achieved, the toolmember 110 is disengaged from implant 10. When the tool 110 is removed,the locking member 80 returns to the back to its initial positionbecause of the arms 82, 84 returning back to their unflexed, at-reststate. The initial position of locking member 80 prevents the gearmember 16 from turning because of the engagement of engagement member 90with the cutouts 73. In that regard, implant 10 is locked from movementwhen the locking member 80 is in its initial position.

The benefit provided by the present locking mechanism is that it allowsfor a positive lock that engages and disengages automatically with theengagement and disengagement of the tool 110 with the implant 10, whichminimizes the steps the surgeon must perform during the procedure.

Referring now to FIGS. 10-13, alternate preferred embodiments ofendplates for the expandable implant 10 are shown. Looking at FIG. 10,in one variation, the endplates 202 and outer member 204 each include atleast one screw hole 206, 208, but, preferably, each include two screwholes. The screw holes 206, 208 are configured and dimensioned toreceive screws 210, 212. In a preferred embodiment, the screw holes 206,208 are angled such that when the screws 210, 212 are seated in thescrew holes 206, 208, the screws 210, 212 will extend outwardly from thesuperior surface 214 of endplate 202 and inferior surface 216 of outermember 204. Endplate 202 and outer member 204 also preferably include alocking element 218, 220 which, in a first position, allow the screws210, 212 to back out from the seated position and, in a second position,block the screws 210, 212 from backing out of the seated position. In anexemplary use, once the implant 200 is installed and expanded to thedesired position, the screws 210, 212 can be installed through the screwholes 206, 208 in such a manner as to purchase into the adjacentvertebral bodies. Once the screws 210, 212 are properly installed,including being engaged with the adjacent vertebral bodies, the lockingelements 218, 220 can be actuated to block the screws 210, 212 frombacking out of their installed position. The inclusion of screws 210,212 in the endplate 202 and the outer member 204 provides for additionalfixation of the implant 200 in the intervertebral space.

Turning to FIGS. 11-13, another preferred embodiment of an endplate 250is shown. The endplate 250 is similar to endplate 20 but includes theadditional functionality of being poly-axially rotatable with respect toan implant. In a preferred embodiment, endplate 250 includes a generallyarcuate extension portion 252 which is received in an interior portion253 of a receiving member 254 in such a manner as to allow the endplate250 to move poly-axially with respect to the receiving member 254.

In a preferred embodiment, the receiving member 254 is received in aninterior portion 255 of a locking ring 256. The receiving member 254preferably includes a neck portion 258 as well as a plurality of tabs260. The neck portion 258 is configured and dimensioned to be receivedwithin a hollow interior of an inner member, for example, in aninterference or snap fit, and the plurality of tabs 260 interdigitatewith tabs to connect and position the receiving member 254 with respectto an inner member. The receiving member 254 further includes aplurality of fingers 262 configured to cooperatively receive theextension portion 252 of endplate 250. A plurality of relief spaces orslots 264 are radially spaced between fingers 262 to allow fingers 262to bend or flex radially.

In a preferred embodiment, the locking ring 256 has a generally annular,c-shape and includes an exterior wall 266, an interior wall 268, andends 277, 279. The interior wall 268 preferably defines and interiorportion 255. In a preferred embodiment, the interior wall 268 includes aplurality of channel 270 which are spaced radially along the lockingring 256. The channels 270 allow the locking ring 256 to bend or flexradially. The ends 277, 279 each include openings 280, 282 which may bepartially threaded. A locking element 284 is configured and dimensionedto be threadingly received in the openings 280, 282. It alsocontemplated that that locking element 284 can engage the ends 277, 279by other non-threaded means, such as a sliding fit.

With continued reference to FIGS. 11-13, in a preferred embodiment, theendplate 250 includes a plurality of mounting holes 286 spaced aroundthe perimeter of the endplate 250 for receiving insertable bone engagingmembers. In one embodiment, bone engaging members, comprise conicalspikes each having a cylindrical base portion configured to fit withinholes 286, for instance, by press-fit or by threaded engagement. Inalternate embodiments, differently shaped bone engaging members may beused, or in other embodiments no bone engaging members may be used.According to one preferred embodiment, endplate 250 has chamfered edges288 around the perimeter to facilitate insertion and/or accommodate theshape of the vertebral bodies which they engage. The superior or boneengaging surfaces 290 of endplate 250 may also include numerous types oftexturing to provide better initial stability and/or grasping contactbetween the end plate and the respective vertebrae. In a preferredembodiment, the texturing is a plurality of teeth 292. In preferredembodiments where the implant is manufactured from PEEK or other plasticmaterials, the endplate 250 may also include radio-opaque material, suchas tantalum markers 294, which aid in providing location markers inradiographic images.

In an exemplary use, during the implant installation and expansion tothe desired position, the endplate 250 can move in poly-axial fashionwith respect to the implant to accommodate the anatomy of the adjacentvertebral body as well as accommodate the natural curvature of thespine, such as kyphosis and lordosis. More specifically, the arcuateextension portion 252 is free to move in the interior portion 253 of thereceiving portion 254. The fingers 262 are generally compliant and canflex to accommodate the movement of the arcuate extension portion 252.Once the desired positioning of the endplate 250 is achieved, theendplate 250 can be locked in place. The endplate 250 is locked in placeby actuating the locking element 284. As the element 284 engages thethreading in opening 280,282 the ends 277, 279 of the locking ring 256are brought closer together contracting the ring 254 and reducing thesize of the interior portion 255. As the ring 254 contracts, the fingers262 of the receiving member 254, abutting against the inner wall 268,are flexed radially inwardly pushing against the extension portion 252.As a result, the endplate 250 is locked in place.

Referring to FIGS. 14-19, another preferred embodiment of an expandablevertebral implant 300 is shown. The implant 300 preferably comprises aninner member 302 which may be telescopingly received within an outermember 304. The implant 300 further comprises a gear member 306generally configured to effect translation of the inner member 302 withrespect to the outer member 304 thereby allowing for expansion andcontraction of the implant 300. The inner member 302, the outer member304, and the gear member 306 are preferably centered along alongitudinal axis 308 and define a hollow interior portion which may befilled with bone material, bone growth factors, bone morphogenicproteins, or other materials for encouraging bone growth, blood vesselgrowth or growth of other tissue through the many apertures in thedevice. In one preferred embodiment, members 302, 304, and 306 are madeof a polyether ether ketone (PEEK) plastic material. There are severalknown advantages of PEEK plastic material including being radiolucent,having a mechanical strength that is close to bone, and may be moreeasily sterilized than other plastics. In alternate preferredembodiments, the members 302, 304, and 306 may be made of a biologicallyinert metal alloys, such as titanium, or other suitable materials.

Referring to FIGS. 14-19, the inner member 302 has a generallycylindrical body 314 with a distal end 312 and a proximal end 326. In apreferred embodiment, the body 314 of the inner member 302 comprises aninner surface 318 and an outer surface 320 and generally defines ahollow interior portion 313 extending axially therethrough. At leastpart of the outer surface 320 preferably includes external threads 322.Located proximate to the distal end 312 of the body 314 are a pluralityof tabs 328 which assist in connecting and positionally locating anendplate 310. In a preferred embodiment, the body 314 is configured anddimensioned to be cooperatively received within outer member 304.

The outer member 304 has a generally cylindrical body 330 with a distalend 332 and a proximal end 334. In a preferred embodiment, the body 330of the outer member 304 comprises an inner surface 336 and an outersurface 338 and generally defines a hollow interior portion 340extending axially therethrough. In one preferred embodiment, extendingfrom the outer surface 338 through the inner surface 336 is at least oneopening 339 configured and dimensioned to allow access to the hollowinterior portion 340. Opening 339 can be used as an access to pack theouter member 304 with bone growth material. The outer surface 338preferably has at least one slot 342 and an opening 344 configured anddimensioned to receive a portion of an implantation tool. In a preferredembodiment, the opening 344 extends from the outer surface 338 to thehollow interior portion 340 and at least a portion of the opening 344 isthreaded. As best seen in FIG. 15, the inner surface 336 includes achannel 347 for receiving a locking member (discussed below). Locatedproximate to the proximal end 334 of the outer member 304 are aplurality of tabs 350 which assist in connecting and positionallylocating an endplate 352. In a preferred embodiment, a lip 352 is formedaround the exterior of the distal end 332 of body 330 and is configuredto cooperatively fit with a portion of the gear member 306. A pluralityof relief spaces or slots 354 are radially spaced around lip 352 tofacilitate a snapping engagement of the lip 352 with the gear member306. In this regard, slots 354 allow the lip 352 to deform slightly andcontract in the radial direction to accommodate gear member 306 to snapon to lip 352. In a preferred embodiment, the interior portion 340 ofbody 330 is configured and dimensioned to cooperatively receive body 314of inner member 302 within outer member 304. In this regard, thedimensions of interior portion 340 of body 330 are greater thandimensions of body 314 of inner member 302.

As best seen in FIGS. 14, 15, and 19, in a preferred embodiment of aprosthetic device 300, the body 314 of the inner member 312 includes aflattened portion 324 which extends at least in part from the distal end312 to the proximal end 326 and includes a base member 327 having atleast one lobe 329 located proximate to the distal end 326 of the body314. Focusing on FIG. 15, the body 330 of the outer member 304 includesa flattened area 346 and at least one depression 348 on the innersurface 336. When the inner member 302 is assembled within the outermember 304, the flattened area 346 of the outer member 304 cooperativelyaligns with the flattened portion 324 of the inner member 302 and the atleast one depression 348 of outer member 304 receives the at least onelobe 329 of the inner member 302. The flattened portion 324 and theflattened area 346 along with the lobes 329 and the depressions 348cooperate to allow the inner member 302 to linearly move with respect tothe outer member 304 but prevent the inner member 302 from rotating withrespect to the outer member 304. In addition, the base member 327 servesas a stop preventing the inner member 302 from rotating to a point ofdisengagement from outer member 304.

Referring now to FIGS. 16-17, a gear member 306 comprises a generallyhollow body 354 extending from a distal end 356 to a proximal end 358with a helical thread 360 along at least part of an inner wall 362 andan array of gear teeth 364 along a portion of the exterior wall 365. Thegear member 306 is generally configured to rotatably connect to thedistal end 332 of the outer member 304 and the internal helical thread360 is configured to engage the external threads 322 of the inner member302 to cause translation of the inner member 302 with respect to theouter member 304. In a preferred embodiment, the gear member 306includes a cylindrical cutout feature 366 extending around the innerwall 354 to cooperatively receive the lip 352 of the outer member 304.In this regard, the gear member 306 may rotate freely with respect tothe outer member 304 while being retained from longitudinal and lateralmovement. In a preferred embodiment, the gear member 306 also includes aseries of engagement members 363 located proximate to the proximal end358 for engaging a portion of a locking ring 371. In a preferredembodiment, the locking ring 371 is configured and dimensioned to bereceived in the gear member 306 and includes a plurality of slots 373for engaging the engagement member 363 on a first end and includes aseries of cutouts 375 for engaging a locking member on a second end. Theengagement members 363 fit within the slots 373 in such a manner as toprevent the locking ring 371 from disengaging from the gear member 306.In one preferred embodiment, the locking ring 371 may be made of adifferent material than the gear member 306. For example, the lockingring may be made from titanium or other biocompatible metal and the gearmember may be made from PEEK or other biocompatible polymer material.

With continued reference to FIGS. 16-17, the gear teeth 364 extendsubstantially from the proximal end 358 to the distal end 356 and extendaround the entire periphery of at least a portion of the exterior wall365. The outer-most external diameter 368 of the gear member 306 issized to be the same as or slightly smaller than the smallest outerdiameter of the endplates 310, 352 and the outer member 304. In thisregard, when the implant 300 is viewed from the end in a planeperpendicular to the longitudinal axis 308, the gear member 306 does notprotrude radially outward from beyond the perimeter of the endplates310, 352.

As shown in FIG. 17, in a preferred embodiment, the gear teeth 364extend a width 370 in a generally radial direction and generally extendradially outward to the outer diameter of the gear member 306. In thisregard, the teeth 364 may be designed to have a width 370 to accommodatethe expected gear forces given the particular gear ratio, types ofmaterial used, and desired overall diameter of prosthetic device 300.One skilled in the art will appreciate that the larger the outerdiameter to which the teeth 364 radially extend, the larger the teeth364 may be designed while still maintaining the same gear ratio. In thisregard, when the teeth 364 are made larger, they generally have a bettermechanical strength. Also, the ability to design larger, wider, andstronger teeth 364 is advantageous for embodiments where the implant 300is made of PEEK, other plastic, or other non-metallic materials that mayhave less mechanical strength than, for instance, titanium.

Furthermore, as described in one embodiment, because the outer-mostdiameter of the gear member 306 may be as large as the outer diameter ofthe endplates 310, 352, and the teeth 364 extend radially to theouter-most diameter of the gear member 306, a larger inner diameter ofthe gear member 306 may be manufactured without compromising mechanicalgear strength. As a result, a larger overall inner diameter of theimplant 300 may be accommodated which allows the packing of more bonematerial therein and facilitates bone fusion once the implant 300 isimplanted.

As seen in FIG. 14, in a preferred embodiment, the teeth 364 are exposedto the exterior of prosthetic device 300. Because the teeth 364 areexposed around the periphery, little to no material is needed to coverup the exposed teeth, which generally makes the implant 300 lighter andeasier to manufacture than prior art devices that require covering thegear teeth. In addition, the gear member 306 is more easily visible by asurgeon and more readily accessible by a rotation tool than devices thathide or cover gear teeth.

Referring to FIGS. 14, 18, and 19, in a preferred embodiment, theimplant 300 also includes a locking member 380. The locking member 380may be provided to substantially restrict all relative movement betweeninner member 302 and outer member 304, when, for example, the desiredexpansion of the prosthetic device 300 has been obtained. The lockingmember 380 has a body portion 382 with an engagement member 384. In apreferred embodiment, the body portion 382 is dimensioned to be flexibleallowing the locking member 380 to flex but return to its originalconfiguration or orientation. The locking member 380 is configured anddimensioned to be received in the channel 347 of the outer member 304 insuch a manner that body portion 382 aligns with opening 344. Theengagement member 384 preferably protrudes upwardly and is configuredand dimensioned to engage the cutouts 375 of the locking ring 371, whichis fixed to the gear member 306, to prevent the gear member 306 fromrotating.

Referring now to FIG. 14, in a preferred embodiment, the endplates 310,352 are shown wherein the endplate 310 connects to the inner member 302and endplate 352 connects to the outer member 304. In a preferredembodiment, endplate 310 includes an extension portion 381 which isreceived in the interior portion 313 of inner member 302, for example,in an interference or snap fit and includes a plurality of tabs 383which interdigitate with tabs 328 to connect and position endplate 310with respect to the inner member 302. Endplate 352 includes a pluralityof tabs 387 which interdigitate with tabs 350 to connect and positionendplate 352 with respect to the outer member 304. The endplates 310,352 also preferably include hollow interior portions 389, 391 which arein fluid communication with the hollow interior portions 313, 340 ofinner member 302 and outer member 304, respectively.

In a preferred embodiment, each endplate 310, 352 is generally annularin shape when viewed from the end or perpendicular to the longitudinalaxis 308. It is, however, contemplated that the endplates 310, 352 canbe other shapes including oblong, elliptical, kidney bean, polygonal, orgeometric. Preferably, the endplates 310, 352 are designed to resembleor mimic the footprint of the vertebral body to which the endplates willengage. In this regard, endplates 310, 352 are configured to engageportions of the vertebrae in a predetermined orientation to maximizecontact of the superior surface of the endplates 310, 352 with bone.

The dimensions of endplates 310, 352 can be varied to accommodate apatient's anatomy. In some embodiments, the endplates 310, 352 have awedge-shaped profile to accommodate the natural curvature of the spine.In anatomical terms, the natural curvature of the lumbar spine isreferred to as lordosis. When implant 300 is to be used in the lumbarregion, the angle formed by the wedge should be approximately between3.5 degrees and 16 degrees so that the wedge shape is a lordotic shapewhich mimics the anatomy of the lumbar spine. In alternate embodiments,the wedge shape profile may result from a gradual increase in heightfrom an anterior side to a posterior side to mimic the naturalcurvature, kyphosis, in other regions of the spine. Thus, in otherembodiments, the angle may be between about −4 degrees and −16 degrees.

As shown in FIG. 14, in a preferred embodiment, the endplates 310, 330include a plurality of mounting holes 382 spaced around the perimeter ofeach endplate 310, 330 for receiving insertable bone engaging members384. In one embodiment, bone engaging members 384, comprise conicalspikes 386 each having a cylindrical base portion 388 configured to fitwithin holes 382, for instance, by press-fit or by threaded engagement.In alternate embodiments, differently shaped bone engaging members 384may be used, or in other embodiments no bone engaging members may beused. Referring again to FIG. 14, according to one embodiment, endplates310, 352 have chamfered edges around the perimeter to facilitateinsertion and/or accommodate the shape of the vertebral bodies whichthey engage. The superior or bone engaging surfaces 392, 394 ofendplates 310, 352 may also include numerous types of texturing toprovide better initial stability and/or grasping contact between the endplate and the respective vertebrae. In a preferred embodiment, thetexturing is a plurality of teeth 396. In preferred embodiments wherethe implant 10 is manufactured from PEEK or other plastic materials, theendplates 310, 352 may also include radio-opaque material, such astantalum markers 398, which aid in providing location markers inradiographic images.

In preferred embodiments, the length, diameter, and shape of prostheticdevice 300 may vary to accommodate different applications, differentprocedures, implantation into different regions of the spine, or size ofvertebral body or bodies being replaced or repaired. For example,implant 300 may be expandable to a longer distance to replace multiplevertebral bodies. Also endplates 310, 352 can be sized and shaped aswell as positioned to accommodate different procedures and approached tothe spine. For example, endplates 310, 352 may be made smaller forsmaller statured patients or for smaller regions of the cervical spine.In addition, it is not required that endplates 310, 352 be shaped andsized identically and in alternate embodiments they can be shaped orsized differently than each other and/or include different bone engagingmembers or texturing.

Turning now to FIGS. 18-19, the implant 300 may be expanded by a tool400 that includes a gear member 402 at its distal end 404. The tool 400extends along a tool axis 405 and in operation the tool 400 isconfigured to engage the implant 300 such that the tool axis 405 isgenerally perpendicular to the longitudinal axis 308. The gear member402 is configured to engage teeth 364 of the gear member 306 such thatwhen the gear member 402 is rotated, the gear member 402 of the implant400 is rotated about the longitudinal axis 18 and the inner member 302translates along the longitudinal axis 308 to either expand or contractthe implant 300. In a preferred embodiment, the tool 400 may include acentral shaft 406 having a threaded distal tip portion 408 that extendsdistally beyond gear member 402 to facilitate location and mounting oftool 400 with the implant 300. The threaded distal tip portion 408preferably includes a generally conical end portion and may beconfigured to extend radially through the opening 344 and threadablyengage opening 344 in the outer member 304.

With continued reference to FIGS. 18-19, in one embodiment of prostheticdevice 300 at least one, but preferably a plurality of mounting featuresor slots 342 are provided along the outer surface 338 of outer member304. The tool 400 includes at least one, but preferably two, arms 410,412 that engage slots 342 for better engagement of the tool 400 with theimplant 300 during insertion of the implant 300. In another preferredembodiment, the tool 400 may include arms 410, 412 that articulate.

In an exemplary use of the tool 400 with the implant 300, the tool 400initially engages the slots 342 of the implant 300 via the arms 410, 412and gear member 402 engages gear member 306 via their respectiveinterdigitating teeth. A control member on the proximal end of the tool400 (not shown) is manipulated to advance the central shaft 406 towardopening 344. The threaded tip portion 408 enters into opening 344engaging the threads in opening 344 as well as engaging the body 382 oflocking member 380. It is also contemplated that the central shaft 406is not movable with respect to the tool 400. In that embodiment, theentire tool 400 is moved so that the central shaft can enter and engagethe opening 344 and the body 382. When threaded tip portion 408 engagesand advances into the opening 344 and pushes against body 382 of thelocking member 380, the locking member 380 is flexed inwardly toward thecenter of the implant 300. As the locking member 380 flexes inwardly,the engagement member 384 disengages from the cutout 375 of the lockingring 371, which is fixed to the gear member 306, allowing the gearmember 306 to rotate freely. The gear member 402 of tool 400 is thenrotated which, in turn, rotates gear member 306. As discussed above, therotation of gear member 306 results in the movement of inner member 302causing the implant 300 to either expand or contract, depending on thedirection the gear member 306 is rotated. Once the desired height forimplant 300 is achieved, the tool member 400 is disengaged from implant300. When the tool 400 is removed, the locking member 380 returns to theback to its initial position because the threaded tip portion 408 is nolonger pushing against the body 382 of the locking member 380 causing itto flex inwardly. The initial position of locking member 380 preventsthe gear member 306 from turning because of the engagement of engagementmember 384 with the cutouts 375 of the locking ring 371. In that regard,implant 300 is locked from movement when the locking member 380 is inits initial position.

The benefit provided by the present locking mechanism is that it allowsfor a positive lock that engages and disengages automatically with theengagement and disengagement of the tool 400 with the implant 300, whichminimizes the steps the surgeon must perform during the procedure.

Referring to FIGS. 20-22, another preferred embodiment of an expandablevertebral implant 500 is shown. Implant 500 is similar to implant 300discussed above. The implant 500 includes an inner member 502 which maybe telescopingly received within an outer member 504. The implant 500further comprises a gear member 506 generally configured to effecttranslation of the inner member 502 with respect to the outer member 504thereby allowing for expansion and contraction of the implant 500. Theinner member 502, the outer member 504, and the gear member 506 arepreferably centered along a longitudinal axis 508 and define a hollowinterior portion which may be filled with bone material, bone growthfactors, bone morphogenic proteins, or other materials for encouragingbone growth, blood vessel growth or growth of other tissue through themany apertures in the device. In addition, the implant 500 may includeone or more endplates 510, 552 configured to engage adjacent vertebrae.

Referring to FIG. 20, the inner member 502 has a generally cylindricalbody 514 with a distal end 512 and a proximal end 526. In a preferredembodiment, the body 514 of the inner member 502 comprises an innersurface 518 and an outer surface 520 and generally defines a hollowinterior portion extending axially therethrough. At least part of theouter surface 520 preferably includes external threads 522. Locatedproximate to the distal end 512 of the body 514 are a plurality of tabs528 which assist in connecting and positionally locating the endplate510. In a preferred embodiment, the body 514 of the inner member 502 isconfigured and dimensioned to be cooperatively received within outermember 504.

The outer member 504 has a generally cylindrical body 530 with a distalend 532 and a proximal end 534. In a preferred embodiment, the body 530of the outer member 504 comprises an inner surface 536 and an outersurface 538 and generally defines a hollow interior portion extendingaxially therethrough. The outer surface 538 may include at least oneslot 542 and an opening 544 configured and dimensioned to receive aportion of an implantation tool. In a preferred embodiment, the opening544 extends from the outer surface 538 to the hollow interior portionand at least a portion of the opening 544 is threaded. The inner surface536 includes a channel for receiving a locking member 580. Locatedproximate to the proximal end 534 of the outer member 504 are aplurality of tabs 550 which assist in connecting and positionallylocating the endplate 552. For example, a lip may be formed around theexterior of the distal end 532 of body 530 and is configured tocooperatively fit with a portion of the gear member 506. A plurality ofrelief spaces or slots may be radially spaced around the lip tofacilitate a snapping engagement of the lip with the gear member 506.The interior portion of the outer member 504 may be configured anddimensioned to cooperatively receive the inner member 502.

As shown in FIG. 22a , the inner member 502 may include at least onelongitudinal groove 622 or a series of grooves extending along a lengthof the inner member 502. In particular, the longitudinal groove 622 mayextend along a portion of the outer surface 520 or the external portionof the inner member 502. The groove 622 may be a cutout extending adepth into the inner member 502 or may extend through the entire wall ofthe inner member 502. The longitudinal groove 622 may be positionedsubstantially parallel to the longitudinal axis 508 of the implant 500.The longitudinal groove 622 is configured to engage a pin 620 protrudingfrom the outer member 504 such that the pin 620, when engaged in thegroove 622, prevents the inner member 502 from translating completelythrough the outer member 504. In other words, the pin 620 aids in theimplant functionality by preventing the inner member 502 from recessingtoo deeply into the outer member 504 or from disassembling from theouter member 504. In addition, the pin 620 is configured to aid inalignment and limit rotation of the second endplate 552.

Referring to FIGS. 22a and 22b , the pin 620 may include a first end 620a and a second end 620 b. The pin 620 may extend through a wall of theouter member 504 such that the second end 620 b is configured to engagethe groove 622 in the inner member 502. The pin 620 may protrude from anouter surface and/or an inner surface of the outer member 504. The pin620 may be configured to fit in one of the gaps between a plurality tabs587 on the distal end 556 of the second endplate 552 to aid in alignmentand limit rotation of the second endplate 552. As shown in FIG. 22b ,the pin 620 may engage with an uppermost surface of the groove 622 toprevent the inner member 504 from translating through an opening in aproximal end 534 of the outer member 504 (e.g., from translatingcompletely through the outer member 504).

The pin 620 may be fixed, pressed, fitted, or machined into the outermember 504. The pin 620 may be a separate piece or may be integral withthe outer member 504. The pin 620 may be positioned transversely to theouter member 504 (e.g., perpendicular to the longitudinal axis 508).Although the pin 620 is depicted as cylindrical in shape, the pin 620may have any suitable shape and form, such as square, rectangular,conical, pyramidal, oblong, polygonal, or other suitable shape orcross-section to engage the groove 622. In addition, the pin 620 mayhave an elongate body, which is solid or hollow therethrough.

The inner member 502 may include additional grooves 622 including asecond longitudinal groove (not shown) positioned substantially parallelto the first groove 622 and configured to receive a second pin 620protruding from the outer member 504. For example, FIG. 21a depicts twopins 620 positioned proximate to the proximal end 534 of the outermember 504, located parallel to one another, and centered along thelongitudinal axis 508 of the implant 500. The pins 620 can function intwo different ways: (1) the pins 620 can aid in alignment of the lowerendplate 552 during its assembly to the outer member 504 by fittingbetween the tabs 587 on the lower endplate 552; and (2) the pins 620serve to prevent downward translation of the inner member 502 within theouter member 504 past a specific point, including preventing disassemblyof the implant 500.

The gear member 506 comprises a generally hollow body 554 extending froma distal end to a proximal end with a helical thread along at least partof an inner wall and an array of gear teeth 564 along a portion of itsexterior wall. The gear member 506 is generally configured to rotatablyconnect to the distal end 532 of the outer member 504 and the internalhelical thread is configured to engage the external threads 522 of theinner member 502 to cause translation of the inner member 502 withrespect to the outer member 504. The gear member 506 may include acylindrical cutout feature extending around the inner wall tocooperatively receive the lip of the outer member 504. In this regard,the gear member 506 may rotate freely with respect to the outer member504 while being retained from longitudinal and lateral movement. In apreferred embodiment, the gear member 506 also includes a series ofengagement members located proximate to the proximal end for engaging aportion of a locking ring 571. In a preferred embodiment, the lockingring 571 is configured and dimensioned to be received in the gear member506 and includes a plurality of slots for engaging the engagement memberon a first end and includes a series of cutouts for engaging a lockingmember 580 on a second end.

The implant 500 may also include a locking member 580. The lockingmember 580 may be provided to substantially restrict all relativemovement between inner member 502 and outer member 504, when, forexample, the desired expansion of the prosthetic device 500 has beenobtained. The locking member 580 has a body portion with an engagementmember 584. In a preferred embodiment, the body portion is dimensionedto be flexible allowing the locking member 580 to flex but return to itsoriginal configuration or orientation. The locking member 580 isconfigured and dimensioned to be received in the channel of the outermember 504 in such a manner that body portion aligns with opening 544.The engagement member 584 preferably protrudes upwardly and isconfigured and dimensioned to engage the cutouts of the locking ring571, which is fixed to the gear member 506, to prevent the gear member506 from rotating.

The endplates 510, 552 are configured to engage portions of thevertebrae in a predetermined orientation to maximize contact of thesuperior surface of the endplates 510, 552 with bone. The upper endplate510 includes a distal end 546 configured to engage the superior vertebraand a proximal end 548 configured to engage the inner member 502. Thelower endplate 552 includes a distal end 556 configured to engage theouter member 504 and a proximal end 558 configured to engage theinferior vertebra. When assembled, endplate 510 connects to the innermember 502 and endplate 552 connects to the outer member 504. Theendplates 510, 552 may be axially applied onto the inner and outermembers 502, 504, respectively, when assembled. In a preferredembodiment, endplate 510 includes an extension portion 581 which is atleast partially received in the interior portion of inner member 502. Inparticular, the extension portion 581 may include a proximal portion ofthe endplate 510 including proximal end 548. The extension portion 581may be recessed compared to the portion of the endplate 510 whichcontacts the vertebra. The extension portion 581 may be generallycylindrical in shape. The extension portion 581 may be received in theinner member 502, for example, in an interference or snap fit. Thedistal end 556 of endplate 552 may include a plurality of tabs 587 whichinterdigitate with tabs 550 to connect and position endplate 552 withrespect to the outer member 504. The endplates 510, 552 also preferablyinclude hollow interior portions which are in fluid communication withthe hollow interior portions of the inner and outer members 502, 504,respectively.

The endplates 510, 552 may be provided with bone engaging members 584.For example, the bone engaging members 584 may comprise conical spikes.In alternate embodiments, differently shaped bone engaging members 584may be used, or in other embodiments no bone engaging members may beused. The endplates 510, 552 may have chamfered edges around theperimeter to facilitate insertion and/or accommodate the shape of thevertebral bodies which they engage. The bone engaging surfaces of theendplates 510, 552 may also include numerous types of texturing toprovide better initial stability and/or grasping contact between the endplate and the respective vertebrae. In a preferred embodiment, thetexturing includes a plurality of teeth 596.

Depending on the orientation and positioning of the implant 500, theendplates 510, 552 may be provided with a certain degree of lordosis orkyphosis to mimic a natural or unnatural curvature of the spine. Inorder to facilitate the proper alignment of the implant 500, endplate510 may be provided with a first series of markings 602 and endplate 552may be provided with a corresponding second series of markings 604. Whenat least one of the first and second series of markings 602, 604 arealigned, the first and second endplates 510, 552 are aligned for aspecific approach to the spine (e.g., anterior implantation) and toprovide the desired lordosis or kyphosis. The marking scheme (e.g.,numbering scheme) aids in assembly of the endplates 510, 552 to theother components of the implant (e.g., the inner and outer members 502,504) by allowing a user to align the markings for varying approaches tothe spine.

The first and second series of markings 602, 604 may include characters,alphanumeric characters, numeric characters, colors, symbols, shapes,words, pictures, or similar indicia. These markings 602, 604 may beetched, engraved, or otherwise marked or applied on the endplates 510,552. The first series of markings 602 preferably includes a plurality ofdifferent markings. In other words, the first series of markings 602preferably includes a plurality of markings that do not repeat and arenot the same. As partially shown in FIG. 20, eight different numericmarkings including sequential numbers one through eight are positionedaround the perimeter of endplate 510.

Similarly, the second series of markings 604 preferably includes aplurality of different markings which correspond to the first series ofmarkings 602. Accordingly, eight different numeric markings includingsequential numbers one through eight, which match the sequential numbersprovided on endplate 510, are positioned around the perimeter ofendplate 552. These markings 602, 604 may be visually aligned with oneanother with or without additional markers on the implant 500. In thisway, when one of the first series of markings 602 is aligned with theone of the second series of markings 604, the endplates 510, 552 arepositioned and aligned for a given implantation approach. As shown inthe embodiment shown in FIG. 20, the number “1” on endplate 510 isaligned with the number “1” on endplate 552. Although depicted asnumeric characters, the first and second series of markings 602, 604 maybe any suitable markings, characters, indicia, or the like that can bevisually identified and aligned to match the first and second endplates510, 552. Table 1 depicts a sample key to identify types of alignmentfor the first and second markings 602, 604 for a user.

TABLE 1 Key Implant Upright Implant Upside-Down Approach Lordosis KeyApproach Lordosis Key Anterior Lordosis 1 Anterior Lordosis 1Anterolateral Right Lordosis 2 Anterolateral Left Lordosis 2 DirectLateral Right Lordosis 3 Direct Lateral Left Lordosis 3 PosterolateralRight Lordosis 4 Posterolateral Left Lordosis 4 Posterolateral LeftLordosis 6 Posterolateral Right Lordosis 6 Direct Lateral Left Lordosis7 Direct Lateral Right Lordosis 7 Anterolateral Left Lordosis 8Anterolateral Right Lordosis 8 Implant Upright Implant Upside-DownApproach Kyphosis Key Approach Kyphosis Key Posterolateral Left Kyphosis2 Posterolateral Right Kyphosis 2 Direct Lateral Left Kyphosis 3 DirectLateral Right Kyphosis 3 Anterolateral Left Kyphosis 4 AnterolateralRight Kyphosis 4 Anterior Kyphosis 5 Anterior Kyphosis 5 AnterolateralRight Kyphosis 6 Anterolateral Left Kyphosis 6 Direct Lateral RightKyphosis 7 Direct Lateral Left Kyphosis 7 Posterolateral Right Kyphosis8 Posterolateral Right Kyphosis 8

The first and second series of markings 602, 604 may be positioned atany suitable location on the implant 500. The first series of markings602 may be positioned at intervals around a perimeter of endplate 510.In particular, the first series of markings 602 may be positioned arounda perimeter of the extension portion 581 of the endplate 510. The firstseries of markings 602 may be offset a distance from the proximal end548 of the endplate 510. The second series of markings 604 may bepositioned at intervals, identical to the first series of markings 602,around a perimeter of endplate 552. In particular, the second series ofmarkings 604 may be positioned proximate to the distal end 556 and theplurality of tabs 587 that connect endplate 552 to the outer member 504.

In order to aid in alignment between the first and second series ofmarkings 602, 604 additional markings may be provided on the endplates510, 552, the inner member 502, the outer member 504, or any othersuitable location along the implant 500. For example, as shown in FIG.21b showing a close-up side view of the top of the implant 500 whenassembled, the inner member 502 may comprise a marking 610 configured toalign the first and second series of markings 602, 604. As shown, themarking 610 may be in the form of an arrow. Thus, the number “1” on theendplate 510 is aligned with the arrow marking 610 on the inner member502, and the opening 544 on the outer member 504, which is configuredand dimensioned to receive a portion of an implantation tool. Similarly,as shown in FIG. 21a showing a close-up side view of the bottom of theimplant 500 when assembled, the outer member 504 may comprise a marking612 configured to align the first and second series of markings 602,604. The marking 612 on the outer member 504 may include a rectangle.The marking 612 may be substantially aligned with the opening 544. Asshown, the rectangular marking 612 may be aligned with the arrow 610 onthe inner member 502 and the number “1” on endplate 552. Thus, thesemarkings 610, 612 assist in aligning the first and second series ofmarkings 602, 604 together.

One or more additional markings 606, 614 may be provided on the firstendplate 510 and one or more additional markings 608 may be provided onthe second endplate 552. For example, markings 606 may be interspersedbetween the series of first markings 602. The markings 606 may be in theform of rectangles which extend along the length of the extensionportion 581 of the endplate 510. Marking 614 may be in the form of asquare positioned near the distal end 546 of the endplate 510. Themarkings 606, 614 may help a user to visually identify alignment, forexample, between one of the markings 602, marking 610, marking 612,and/or marking 604. Similarly, a marking 608 may be positioned beneath aprimary marking 604 to identify the most common alignment betweenmarking 604 for number “1”, marking 612, marking 610, and/or marking602. Any suitable type, number, and position of markings 602, 604, 606,608, 610, and 612 may be selected to achieve the pre-determinedalignment of the implant 500 for a given implantation approach and thedesired degree of lordosis or kyphosis.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations can be made thereto by those skilled in the art withoutdeparting from the scope of the invention as set forth in the claims.

What is claimed is:
 1. An expandable prosthetic implant for engagementbetween vertebrae, comprising: an inner member having a hollow interiorportion and an external portion; a first endplate configured to engage afirst vertebral body connected to the inner member, the first endplatecomprising a first series of markings; an outer member having a hollowinterior portion configured to coaxially receive the inner membertherein, wherein the inner and outer members are moveable relative toeach other along a longitudinal axis; a gear member positioned coaxialto the inner member and outer member and axially fixed to the outermember; and a second endplate configured to engage a second vertebralbody connected to the outer member, the second endplate comprising asecond series of markings, wherein when at least one of the first andsecond series of markings are aligned, the first and second endplatesare aligned for a specific approach.
 2. The implant of claim 1, whereinthe first and second series of markings include alphanumeric characters,numeric characters, colors, symbols, shapes, words, or pictures.
 3. Theimplant of claim 1, wherein the first series of markings includes aplurality of different markings.
 4. The implant of claim 1, wherein thesecond series of markings includes a plurality of different markingswhich correspond to the first series of markings.
 5. The implant ofclaim 1, wherein the first series of markings are positioned around aperimeter of an extension portion of the first endplate.
 6. The implantof claim 1, wherein the second series of markings are positioned arounda perimeter of the second endplate proximate to a plurality of tabs thatconnect the second endplate to the outer member.
 7. The implant of claim1, wherein a third marking is provided on the inner or outer members toaid in alignment.
 8. The implant of claim 1 further comprising a lockingmember configured to restrict relative movement between the inner memberand the outer member, wherein the locking member is configured to bereceived in the outer member, and wherein the locking member includes anengagement member that engages the gear member to prevent rotation ofthe gear member.
 9. The implant of claim 8, wherein the engagementmember engages a cutout formed in the gear member to prevent rotation ofthe gear member.
 10. The implant of claim 1, wherein the gear memberincludes gear teeth extending around a perimeter of the gear member, thegear teeth extending from a proximal end of the gear member to a distalend of the gear member.
 11. An expandable prosthetic implant forengagement between vertebrae, comprising: an inner member having ahollow interior portion and an external portion, the inner membercomprising a longitudinal groove extending along a length of the innermember; a first endplate configured to engage a first vertebral bodyconnected to the inner member, the first endplate comprising a firstseries of markings; an outer member having a hollow interior portionconfigured to coaxially receive the inner member therein, wherein theinner and outer members are moveable relative to each other along alongitudinal axis from a first position to a second position; a pinhaving a first end and a second end, the pin extending through the outermember, and the second end configured to engage the groove in the innermember; a gear member positioned coaxial to the inner member and outermember and axially fixed to the outer member; and a second endplateconfigured to engage a second vertebral body connected to the outermember, the second endplate comprising a second series of markings,wherein when at least one of the first and second series of markings arealigned, the first and second endplates are aligned for a specificapproach.
 12. The implant of claim 11, wherein the first and secondseries of markings include alphanumeric characters, numeric characters,colors, symbols, shapes, words, or pictures.
 13. The implant of claim11, wherein the first series of markings includes a plurality ofdifferent markings.
 14. The implant of claim 11, wherein the secondseries of markings includes a plurality of different markings whichcorrespond to the first series of markings.
 15. The implant of claim 11,wherein the first series of markings are positioned around a perimeterof an extension portion of the first endplate.
 16. The implant of claim11, wherein the second series of markings are positioned around aperimeter of the second endplate proximate to a plurality of tabs thatconnect the second endplate to the outer member.
 17. The implant ofclaim 11, wherein a third marking is provided on the inner or outermembers to aid in alignment.
 18. The implant of claim 11 furthercomprising a locking member configured to restrict relative movementbetween the inner member and the outer member, wherein the lockingmember is configured to be received in the outer member.
 19. Anexpandable prosthetic implant for engagement between vertebrae,comprising: an inner member having a hollow interior portion an externalportion, the inner member comprising a longitudinal groove extendingalong a length of the inner member; a first endplate configured toengage a first vertebral body connected to the inner member, the firstendplate comprising a first series of markings; an outer member having ahollow interior portion configured to coaxially receive the inner membertherein, wherein the inner and outer members are moveable relative toeach other along a longitudinal axis from a first position to a secondposition; a pin having a first end and a second end, the pin extendingthrough the outer member, and the second end configured to engage thegroove in the inner member when the inner and outer members are in thefirst position; a gear member position coaxial to the inner member andouter member and axially fixed to the outer member; and a secondendplate configured to engage a second vertebral body connected to theouter member, the second endplate comprising a second series ofmarkings, wherein when at least one of the first and second series ofmarkings are aligned, the first and second endplates are aligned for aspecific approach.
 20. The implant of claim 19, wherein a third markingis provided on the inner or outer members to aid in alignment.